check / repair

sudo btrfs check /dev/sdc1
sudo btrfs check --repair /dev/sdc1
sudo btrfs check --clear-space-cache v1|v2 /dev/sdc1

subvolume

btrfs subvolume create current

btrfs subvolume snapshot    current 2018-01-04
btrfs subvolume snapshot -r current 2018-01-04  # read only

sudo btrfs subvolume list .
# restrict list to `dir`, given that `dir` is a subvolume on its own
sudo btrfs subvolume list -o dir/

sudo btrfs subvolume delete 2018-01-04

# set / unset readonly
btrfs property set -ts subvol ro false

send/receive

• src needs to be subvolume
• have to create readonly snapshot of src before syncing
• send compares two readonly snapshots, need to keep old one around

• send seems to be root, receive also. confirm?

  init

  btrfs subvolume create src btrfs subvolume snapshot -r src src-date -Iminutes sudo btrfs send src-2018-01-18T14\:52+01\:00 | sudo btrfs receive backup/

  increment

  btrfs subvolume snapshot -r src src-date -Iminutes sudo btrfs send -p src-2018-01-18T14\:52+01\:00 src-2018-01-18T14\:57+01\:00 | sudo btrfs receive backup/

raid

btrfs filesystem show
btrfs filesystem df /mnt/
sudo mkfs.btrfs /dev/sda1 -L label
sudo btrfs device add /dev/sda2 /mnt/
sudo btrfs balance start -dconvert=raid1 -mconvert=raid1 /mnt/
sudo btrfs device delete /dev/sda1 /mnt/
sudo btrfs balance pause /mnt/

sudo btrfs balance start -f -mconvert=single -dconvert=single /mountpoint
sudo btrfs device remove missing /mountpoint
sudo btrfs balance start -mconvert=dup /mountpoint